Noise-induced hearing loss (NIHL) is hearing loss caused by loud sounds. NIHL can be caused by a single exposure to an intense “impulse” sound, such as an explosion, or by repeated or continuous exposure to loud sounds over an extended period of time, such as noise generated in a woodworking shop. NIHL is not understood completely, but current models of NIHL suggest that sounds at levels above about 85 dB are likely to damage sensitive structures in the inner ear, leading to hearing loss. Current models of NIHL also suggest that extremely loud impulsive sounds (sounds with rise times shorter than about one second and peak amplitudes over about 85 dB) cause damage more quickly than softer sounds with longer rise times. Loud, impulsive sounds may also cause tinnitus, a condition in which the afflicted person perceives ringing in the ears even under silent conditions.
NIHL affects up to 15% of Americans between the ages of 20 and 69, or about 26 million people total. More than 30,000 cases of noise-induced hearing injuries were reported among active-duty soldiers, sailors, airmen, and Marines in 2010. The number of new tinnitus incidents per year increased 42% from 2007-2010 among service members. In 2009 alone, the government made more than 100,000 new service-connected disability awards for tinnitus and hearing loss. About 10% of veterans' disability payments made for tinnitus and hearing loss; in 2013, hearing loss and tinnitus disability payments totaled about $850,000,000 per year.